Remote unit for communicating with base stations and terminal devices

ABSTRACT

A remote unit of a distributed antenna system includes: a transceiver configured to communicate RF signals between a master unit of the distributed antenna system and a terminal device, and receive downlink RF signals from a base station; and signal processing circuitry configured to provide downlink signals to the master unit. The remote unit receives instructions from a host unit of the distributed antenna system to establish a communication link with the base station in response to detecting a malfunction with respect to an additional communication link between the master unit and an additional base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 14/790,053filed Jul. 2, 2015 and titled “REMOTE UNIT FOR COMMUNICATING WITH BASESTATIONS AND TERMINAL DEVICES”, which is a continuation of U.S. patentapplication Ser. No. 14/213,168 filed Mar. 14, 2014 and titled “RemoteUnit for Communicating with Base Stations and Terminal Devices”, whichclaims priority to U.S. Provisional Application Ser. No. 61/790,515filed Mar. 15, 2013 and titled “Remote Antenna Unit for Communicatingwith Base Stations and Mobile Communication Devices”, the contents ofeach of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to telecommunications systemsand more particularly (although not necessarily exclusively) to remoteunits of distributed antenna systems that can communicate with basestations and terminal devices.

BACKGROUND

A distributed antenna system (“DAS”) may include master units and remoteunits. Master units may be connected to base stations. Master unitsreceive downlink signals from base station and distribute downlinksignals in analog or digital format to multiple remote units. The remoteunits transmit downlink signals to terminal devices within coverageareas serviced by the remote units. In the uplink direction, signalsfrom terminal devices may be received by the remote units. The remoteunits may combine uplink signals and transmit the combined uplinksignals to master units. Master units may transmit uplink signals to theserving base stations.

SUMMARY

Certain aspects and features of the present invention are directed todistributed antenna systems in which remote units can communicate withbase stations and terminal devices.

In one aspect, a distributed antenna system is provided. The distributedantenna system can include a master unit that is communicatively coupledto a first remote unit and a second remote unit. The first remote unitcan communicate RF signals between the master unit and a terminaldevice. The first remote unit can also receive analog downlink RFsignals from a base station and convert the analog downlink RF signalsto digital downlink signals. The first remote unit can provide thedigital downlink signals to the master unit. The master unit cantransmit the digital downlink signals received from the first remoteunit to the second remote unit.

In another aspect, a remote unit of a distributed antenna system isprovided. The remote unit can include a signal processing module and atransceiver. The transceiver can communicate RF signals between a masterunit of the distributed antenna system and a terminal device. Thetransceiver can also receive analog downlink RF signals from a basestation. The signal processing module can convert the analog downlink RFsignals to digital downlink signals and provide the digital downlinksignals to the master unit.

In another aspect, a distributed antenna system for providingdevice-to-device communication is provided. The distributed antennasystem can include a first remote unit, a second remote unit, and amaster unit that is communicatively coupled to the first and secondremote units. The first remote unit can receive a signal from a firstterminal device. The master unit can receive the signal from the firstremote unit and provide the signal to the second remote unit fortransmission to the second terminal device. The second remote unit cantransmit the signal to a second terminal device.

These illustrative aspects and features are mentioned not to limit ordefine the disclosure, but to provide examples to aid understanding ofthe concepts disclosed in this application. Other aspects, advantages,and features of the present disclosure will become apparent after reviewof the entire application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting an example of a distributed antennasystem that can include a donor remote unit for communicating with basestations according to one aspect of the present disclosure.

FIG. 2 is a block diagram depicting the donor remote unit of FIG. 1according to one aspect of the present disclosure.

FIG. 3 is a block diagram depicting an example of the donor remote unitof FIG. 2 with multiple duplexers according to one aspect of the presentdisclosure.

FIG. 4 is a block diagram depicting an alternative example of the donorremote unit of FIG. 2 with a configurable isolation sub-system forcommunicating in different frequency bands according to one aspect.

FIG. 5 is a flow chart depicting a process for using the donor remoteunit of FIG. 1 to compensate for a base station malfunction according toone aspect of the present disclosure.

FIG. 6 is a block diagram depicting a remote unit configured fordevice-to-device communication according to one aspect of the presentdisclosure.

DETAILED DESCRIPTION

A remote unit of a distributed antenna system (“DAS”) is disclosed thatcan communicate RF signals with base stations in addition tocommunicating RF signals with terminal devices in a coverage zoneserviced by the remote unit. In some aspects, a master unit can routesignals received from the remote unit to other remote units fortransmission to terminal devices.

In accordance with some aspects, a donor remote unit can receive bothuplink signals from terminal devices and downlink signals from basestations. The donor remote unit can transmit downlink signals receivedfrom base stations to a master unit for distribution via the DAS. Thedonor remote unit can also receive downlink signals from a master unitand transmit the downlink signals to terminal devices in a coverage zoneserviced by the donor remote unit. In some aspects, the donor remoteunit can also transmit the signals received from a base station to otherremote units for transmission to terminal devices in other coveragezones serviced by the other remote units.

As used herein, the term “donor remote unit” can refer to any remoteunit that can include or be communicatively coupled to one or moreantennas and that can be configured to wirelessly receive downlinksignals from a base station and to wirelessly receive uplink signalsfrom terminal devices. For example, a donor remote unit can include atransceiver that is tuned for wirelessly receiving downlink signals in afrequency band used by a base station. The donor remote unit can providean RF link between the DAS and another base station in addition to thebase stations in communication with the master unit of the DAS. Forexample, a donor remote unit can receive signals in an analog RF formatfrom a base station and provide signals in a digital format to one ormore devices in the DAS via a direct connection. For cases in which fewterminal devices are served by an operator within a coverage area of theDAS, a donor remote unit can provide an RF link to a macrocell servicedby a base station in or near the coverage area of the DAS. The RF linkprovided by the donor remote unit can reduce or eliminate costsassociated with installing additional base stations to service a smallernumber of terminal devices.

As used herein, the term “terminal device” can refer to an electronicdevice used to communicate voice and/or data via a telecommunicationssystem, such as (but not limited to) a small cell network or othercellular network. Other terminology used to refer to terminal devicesand non-limiting examples of such devices can include mobile stations,mobile devices, access terminals, subscriber stations, terminal mobileterminals, remote stations, user terminals, terminals, subscriber units,cellular phones, smart phones, personal digital assistants (“PDAs”),laptop computers, netbooks, e-readers, wireless modems, etc.

The RF link provided by the donor remote unit can reduce or eliminatethe need to use a separate RF repeater to receive signals from a nearbymacrocell and transmit the received signals to the DAS. A donor remoteunit may be smaller than a repeater unit. The smaller size of a donorremote unit may allow the donor remote unit to be more easily positionedin different coverage areas than a repeater.

In additional or alternative aspects, remote units for a DAS can beconfigured for device-to-device communication between terminal devicesin a coverage area serviced by the DAS. A master unit or other unit inthe DAS can receive signals within a defined bandwidth from multipleremote units. The level of the signals within the bandwidth can becompared with a threshold signal level. Signals having a signal levelabove the threshold signal level can be summed or otherwise combined.The combined signals can be routed to remote units whose signal level isbelow the threshold. The combined signal can be transmitted by theremote units. In some aspects, a frequency shift can be applied to thecombined signal prior to transmission by the remote units.

As used herein, the term “device-to-device communication” can refer to amode of communication between or among terminal devices that communicatevia a DAS in which the signal traffic from one terminal device toanother terminal device does not pass through a centralized base stationor other device in the telecommunication system. Signal traffic caninclude voice communications or data communications intended forconsumption by a user of a terminal device. Device-to-devicecommunication may be implemented in a DAS by receiving signals from afirst terminal device at a first remote unit, providing the receivedsignals to a second remote unit via a master unit or extension unit, andtransmitting the signals from the second remote unit to a secondterminal device.

Detailed descriptions of certain examples are discussed below. Theseillustrative examples are given to introduce the reader to the generalsubject matter discussed here and are not intended to limit the scope ofthe disclosed concepts. The following sections describe variousadditional aspects and examples with reference to the drawings in whichlike numerals indicate like elements, and directional descriptions areused to describe the illustrative examples but, like the illustrativeexamples, should not be used to limit the present disclosure.

FIG. 1 is a block diagram depicting an example of a DAS 100 that caninclude a donor remote unit 104 for communicating with base stationsaccording to one aspect.

The DAS 100 can include a master unit 102, an extension unit 103, adonor remote unit 104, and remote units 106 a, 106 b. The donor remoteunit 104 and remote units 106 a, 106 b can provide signal coverage toterminal devices positioned in respective coverage zones 108, 110, and112.

The master unit 102 can receive downlink signals from a base station 114and transmit uplink signals to the base station 114. Any suitablecommunication link can be used for communication between the basestation 114 and the master unit 102, such as (but not limited to) adirect connection or a wireless connection. A direct connection caninclude, for example, a connection via a copper, optical fiber, or othersuitable communication medium. In some aspects, the master unit 102 caninclude an external repeater or internal RF transceiver included on adonor card to communicate with the base stations. In some aspects, themaster unit 102 can combine downlink signals received from differentbase stations 114. The master unit 102 can transmit the combineddownlink signals to one or more of the donor remote unit 104 and theremote units 106 a, 106 b.

In some aspects, the master unit 102 can be connected to remote unitsvia one or more extension units or other intermediate devices. Forexample, FIG. 1 depicts a master unit 102 that is communicativelycoupled to an extension unit 103. The extension unit 103 iscommunicatively coupled to the donor remote unit 104 and the remote unit106 a. In additional or alternative aspects, the master unit 102 can beconnected to remote units directly without using extension units orother intermediate devices. For example, FIG. 1 depicts a master unit102 that is communicatively coupled to a remote unit 106 b without usingan extension unit.

The donor remote unit 104 and the remote units 106 a, 106 b can providesignal coverage in coverage zones 108, 110, 112 by transmitting downlinksignals to terminal devices and receiving uplink signals from theterminal devices. The donor remote unit 104 and the remote units 106 a,106 b can transmit uplink signals to the master unit 102. The masterunit 102 can combine uplink signals received from the donor remote unit104 and the remote units 106 a, 106 b for transmission to the basestation 114.

For illustrative purposes, FIG. 1 depicts a DAS 100 that communicateswith two base stations 114, 116 and that includes a single master unit102, a single extension unit 103, a single donor remote unit 104, andtwo remote units 106 a, 106 b. However, a DAS 100 can communicate withany number of base stations and can include any suitable number ofmaster units 102, extension units 103, donor remote units 104, andremote units 106 a, 106 b. In some aspects, a DAS 100 can omit one ormore of the extension unit 103 or the remote units 106 a, 106 b.

The donor remote unit 104 can communicate with both the master unit 102(via the extension unit 103) and a base station 116 within atransmission range of the coverage zone 108. For example, the donorremote unit 104 can receive downlink RF signals from the base station116 and transmit uplink RF signals to the base station 116.Communicating RF signals with the base station 116 can allow the donorremote unit 104 to operate as an RF donor pickup transceiver in additionto a mobile-side transceiver. The donor remote unit 104 can communicatedownlink signals received from the base station 116 to the master unit102.

The master unit 102 can combine the downlink signals received from thedonor remote unit 104 with downlink signals in the same frequency bandreceived from other base stations. The master unit 102 can communicatethe combined downlink signal to one or more of the other remote units106 a, 106 b. The downlink signal can be transmitted by the other remoteunits 106 a, 106 b.

In a non-limiting example, the DAS 100 depicted in FIG. 1 can be used toprovide signal coverage for a coverage area serviced by multiple basestations 114 in communication with the master unit 102 and a neighboringbase station 116 (such as, but not limited to, a macrocell base station)in communication with the donor remote unit 104. A first base station114 that is communicatively coupled to the master unit 102 may operatein the sub-band A of frequency band 1. A second base station 114 that iscommunicatively coupled to the master unit 102 may operate in thesub-band B of frequency band 1. A third base station 114 that iscommunicatively coupled to the master unit 102 may operate in thesub-band C of frequency band 2. The macrocell base station 116 mayoperate in the sub-band D of frequency band 2. The master unit 102 cancombine signals received from the first and second base stations 114into a single signal in frequency band 1. The combined signal infrequency band 1 can include the sub-bands A and B. The master unit 102can transmit the combined signal having frequencies in the sub-bands Aand B of frequency band 1 to remote units 106 a, 106 b in the respectivecoverage zones 110, 112 of the DAS 100.

The donor remote unit 104 can receive signals in frequency band 2. Thedonor remote unit 104 can isolate signals in a sub-band D of frequencyband 2 by applying a bandpass filter that attenuates signals havingfrequencies outside of the sub-band D. The donor remote unit 104 cantransmit the signals in the sub-band D to the master unit 102 via theextension unit 103. The master unit 102 can combine signals in thesub-band C of frequency band 2 received from the third base station 114with signals in the sub-band D received from the macrocell base stationvia the donor remote unit 104. The master unit 102 can transmit thecombined signal having frequencies in the sub-bands C and D of frequencyband 2 to remote units 106 a, 106 b. The master unit 102 can alsotransmit signals having frequencies in the sub-band C of frequency band2 to the donor remote unit 104 for transmission to terminal devices.

FIG. 2 is a block diagram depicting an example of the donor remote unit104 according to one aspect. The donor remote unit 104 can include atransceiver 202, a processor 204, and an signal processing module 208.

The transceiver 202 can be configured to receive downlink RF signalsfrom a base station and transmit uplink RF signals to the base station.In some aspects, the transceiver 202 can be tuned to differentfrequencies based on command signals received from the processor 204.

The processor 204 can include any device suitable for executing programinstructions to control operation of the donor remote unit 104. Examplesof processor 204 include a microprocessor, an application-specificintegrated circuit (“ASIC”), a field-programmable gate array (“FPGA”),or other suitable processor. The processor 204 may include one processoror any number of processors.

The donor remote unit 104 can communicate with the master unit 102 viaany suitable signal processing module 208, such as (but not limited to)a physical layer transceiver or other suitable component configured forcommunicating with a master unit 102. The signal processing module 208can process uplink and downlink signals for communication with themaster unit 102 or extension unit 103. The signal processing module 208can include one or more digital components or devices, one or moreanalog components or devices, or any combination thereof forcommunicating signals between the donor remote unit 104 and the masterunit 102 or extension unit 103. For example, the signal processingmodule 208 can include one or more digital signal processors, one ormore filters, one or more digital-to-analog converters, one or moreanalog-to-digital converters, etc. The signal processing module 208 canconvert analog downlink signals received from a base station 116 intodigital downlink signals to be provided from the donor remote unit 104to the master unit 102.

In some aspects, the donor remote unit 104 can be configured to receiveboth uplink signal and signals from other base station by using atransceiver 202 that does not include a duplexer. In some remote unitsthat do not receive RF downlink signals transmitted by base stations, afixed duplexer may provide isolation between transmit signals inreceived signals. Using a transceiver 202 that does not include aduplexer can allow a receiver component of the transceiver 202 to betuned to receive signals in any frequency band, including one or morefrequency bands used by the base station 116.

In other aspects, the donor remote unit 104 can include at least twoduplexers. For example, FIG. 3 is a block diagram depicting an exampleof a donor remote unit 104 that includes multiple duplexers according toone aspect. The donor remote unit depicted in FIG. 2 includes a mobilecommunication duplexer 302 and a base station communication duplexer304. The mobile communication duplexer 302 can be used for communicationwith terminal devices. The mobile communication duplexer 302 can beconfigured to provide isolation between analog RF uplink signalsreceived from one or more terminal devices and analog RF downlinksignals transmitted to the one or more terminal devices. The basestation communication duplexer 304 can be used for communication with abase station. The base station communication duplexer 304 can beconfigured to provide isolation between analog RF downlink signals (e.g.analog downlink RF signals) received from a base station 116 and othersignals transmitted by the donor remote unit 104 (e.g., analog RF uplinksignals transmitted to the base station 116, analog RF downlink signalstransmitted to terminal devices, etc.).

In other aspects, the donor remote unit 104 can include a configurableisolation sub-system. For example, FIG. 4 is a block diagram depictingan alternative example of a donor remote unit 104 that includestransceiver 202′ with a configurable isolation sub-system 402 forcommunicating in different frequency bands according to one aspect. Theconfigurable isolation sub-system 402 can be configured to provideisolation between signals transmitted to terminal devices and signalsreceived from the terminal devices. The configuration of theconfigurable isolation sub-system 402 can be modified to allow the donorremote unit 104 to communicate with one or more neighboring basestations 116.

In some aspects, the configurable isolation sub-system 402 can include asingle-step configurable filter that can include one or more bandpassfilters. The desired downlink frequency band of a single-stepconfigurable filter can be manually selected in a single physical step,such as (but not limited to) using a switch matrix to select a channelcorresponding to a particular frequency band on a multi-channel switchfilter bank.

In additional or alternative aspects, the configurable isolationsub-system 402 can include an electronically configurable filter. Anelectronically configurable filter may include one or bandpass filtersthat can be configured electronically. Configuring the filter caninclude receiving an electronic control signal and responding to theelectronic control signal by changing the frequency responseaccordingly. The frequency response may be the desired frequency band tobe passed. The electronic control signal may be received from anexternal controller. The electronically configurable filter can includea microprocessor or similar device that can respond to the electroniccontrol signal by configuring the electronically configurable filter tohave a desired frequency response. In some aspects, a bandpass filtercan include one or more varactor diodes. The frequency response of thebandpass filter can be adjusted by varying the capacitance of one ormore varactor diodes in response to the electronic control signal. Thecapacitance of the varactor diodes can be varied by applying varyinginput voltages to terminals of the varactor diodes. Altering thecapacitance of one or more varactor diodes can alter both the centerfrequency and bandwidth of the bandpass filter. In some aspects, thesource of the applied voltage may be disposed in the electronicallyconfigurable filter, with applied voltage levels controlled by themicroprocessor in response to an electronic control signal from theexternal controller. In other aspects, the source of the applied voltagemay be an external device controlled by the external controller.

In some aspects, a DAS 100 can use donor remote units 104 forcommunication with base stations without using a direct connectionbetween a master unit 102 and one or more base stations 114. Forexample, a DAS 100 may include multiple donor remote units 104 that cancommunicate with base stations 116 via a wireless RF communication linkor other suitable wireless link. Such a configuration can be used for aDAS 100 servicing a coverage area in which a preferable location toreceive RF signals from one base station is different from a preferablelocation to receive RF signals from a different base station. Such aconfiguration can also be used for a DAS 100 using n×n multiple-inputand multiple-output (“MIMO”) systems, in which n donor remote units 104can be positioned at different locations for receiving MIMO signals withsufficient spatial diversity. Using donor remote units 104 forcommunication with base stations 116 rather than using a directconnection between a master unit 102 and base stations 114 can extendcoverage for public safety communication systems or othertelecommunication systems having reduced capacity (i.e., fewer availablechannels and/or frequency bands).

In additional or alternative aspects, the donor remote unit 104 can beused to increase the reliability of coverage provided by a DAS 100. Forexample, a base station 114 connected to the master unit 102 mayexperience a malfunction that prevents or degrades signal coverageprovided by the base station 114. A malfunction can be caused by eventssuch as construction or other operations causing a cable link to besevered, an equipment failure in the base station 114, etc.

In a non-limiting example, a DAS 100 can have a standard operation modein the absence of a base station malfunction and an auxiliary mode ofoperation in the presence of a base station malfunction. In the standardoperation mode, the donor remote unit 104 can be configured to receivedownlink signals from the master unit 102 and to ignore downlink signaltraffic from a neighboring base station 116. In the auxiliary mode, thedonor remote unit 104 can be configured to establish a communicationlink with the neighboring base station 116 for receiving downlinktraffic. Establishing such a communication link with the neighboringbase station 116 can reduce or prevent interruptions of at least sometelecommunication services in the coverage area of the DAS 100. Forexample, some telecommunications services (e.g., normal voice calls,etc.) provided by the base station 114 may be interrupted by amalfunction with respect to the base station 114. The auxiliary mode canbe used to provide a subset of telecommunication services (e.g., publicsafety services) that can be accessed via the neighboring base station116.

FIG. 5 is a flow chart depicting a process 500 for using the donorremote unit 104 to compensate for a base station malfunction accordingto one aspect. The process 500 is described with respect to the systemdepicted in FIG. 1. Other implementations, however, are possible.

The process 500 involves determining that a malfunction has occurredwith respect to a base station 114 in communication with a master unit102 of a DAS 100, as depicted at block 510. In some aspects, the masterunit 102 can determine that a malfunction has occurred based on a lossof communication with the base station 114. In one non-limiting example,the master unit 102 can determine that the malfunction has occurredbased on an absence of downlink traffic from the base station 114 for anamount of time exceeding a threshold amount of time. In anothernon-limiting example, the master unit 102 can determine that themalfunction has occurred based on a failure of the base station 114 torespond to signaling or other control communications from the masterunit 102 that are used for establishing or maintaining a communicationlink between the base station 114 and the master unit 102.

In some aspects, one or more devices in the DAS 100 can provide anotification that the base station 114 is malfunctioning. For example,one or more of the master unit 102 or the donor remote unit 104 cangenerate an alarm notification in response to the donor remote unit 104being used to provide signal coverage in the DAS 100. Non-limitingexamples of such an alarm notification include a data messagetransmitted to a communication device or outputted in a graphicalinterface, an audible indicator generated by one or more of the masterunit 102 or the donor remote unit 104, a visual indicator (e.g., aflashing light) generated by one or more of the master unit 102 or thedonor remote unit 104, etc.

The process 500 also involves configuring one or more remote units toidentify a neighboring base station near a coverage area of the DAS 100by scanning downlink frequency bands, as depicted at block 520. Forexample, a DAS 100 may include multiple donor remote units 104. A masterunit 102 can respond determining the base station malfunction byproviding control signals to the multiple donor remote units 104 tosearch for neighboring base stations 116. A neighboring base station caninclude any base station from which signals having specified signalcriteria can be received by one or more donor remote units 104. For eachdonor remote unit 104 that receives the control signal from the masterunit, a respective processor 204 can generate an additional controlsignal that instructs a respective transceiver 202 to scan one or morefrequency bands for downlink signals or other signals that aretransmitted by a base station 116. The transceiver 202 can be tuned orotherwise configured to receive signals in one or more frequency bandsspecified by the control signal. The processor 204 can analyze signaltraffic in the one or more scanned frequency bands to identify one ormore frequencies used by the base station 116 to transmit downlinksignals.

The process 500 also involves selecting at least one of the remote unitsas a donor remote unit based on the selected remote unit receivingdownlink signals from the neighboring base station that meet a specifiedsignal criteria, as depicted at block 530. For example, at least twodonor remote units 104 may be within transmission range of a neighboringbase station 116. One of the donor remote units 104 may receive signalsfrom the neighboring base station 116 that satisfy the signal criteriaand the other donor remote unit 104 may receive signals from theneighboring base station 116 that fail to satisfy the signal criteria.Non-limiting examples of satisfying the signal criteria include asexceeding a threshold signal level, having noise below a threshold noiselevel or satisfying another quality parameter, etc. The master unit 102or another control device in the DAS 100 can select the donor remoteunit 104 that receives signals from the neighboring base station 116that satisfy the signal criteria to establish a communication link withthe neighboring base station 118. The donor remote unit 104 thatreceives signals from the neighboring base station 116 failing tosatisfy the signal criteria can be used to communicate signals withterminal devices in the coverage area of the DAS 100.

The process 500 also involves configuring the selected remote unit toestablish a communication link with the neighboring base station 116, asdepicted at block 540. For example, a selected donor remote unit 104 canconfigure its transceiver 202 to receive downlink signals transmitted bythe neighboring base station 116 and to transmit uplink signals receivedfrom the master unit 102 to the neighboring base station 116.

The process 500 also involves configuring the DAS 100 to provide signalsreceived from the neighboring base station 116 to the other remote unitsin the DAS 100, as depicted at block 550. In some aspects, the masterunit 102 can be configured in the auxiliary mode to utilize the signalsreceived from the donor remote unit 104 as downlink signals. The masterunit 102 can process the signals received from the donor remote unit 104in the same manner that the master unit 102 would process signalsreceived from the base station 114. The master unit 102 can provide thesignal received from the donor remote unit 104 to one or more remoteunits 106 a, 106 b.

In additional or alternative aspects, an extension unit 103 incommunication with the donor remote unit 104 can be used to provide thedonor signal to one or more remote units that are communicativelycoupled to the extension unit 103.

The process 500 also involves determining that the malfunction of thebase station 114 has ceased, as depicted at block 560. For example, themaster unit 102 can determine that the malfunction has ceased based onreceiving downlink traffic from the base station 114 or receiving othersignal traffic from the base station 114.

The process 500 also involves configuring the donor remote unit 104 toterminate the communication link with the neighboring base station 118in response to determining that the malfunction has ceased, as depictedat block 570. For example, a control signal can be provided to the donorremote unit 104 that is selected to receive signals from the basestation 116 in auxiliary mode. The control signal can notify the donorremote unit 104 to switch from auxiliary mode to standard operationmode. The processor 204 of the donor remote unit 104 can respond to thecontrol signal by configuring the transceiver 202 to cease communicatingsignals with the base station 116.

In some aspects, the DAS 100 can automatically switch to an auxiliarymode. In other aspects, the DAS 100 can be switched to an auxiliary modeby an operator performing one or more operations to reconfigure one ormore of the master unit 102 and the donor remote units 104.

In additional or alternative aspects, remote units can be configured toprovide device-to-device communication between terminal devices. Forexample, FIG. 6 is a block diagram depicting an example of a remote unit602 configured for device-to-device communication according to oneaspect. The remote unit 602 depicted in FIG. 6 can be included in theDAS 100 and can be communicatively coupled to the master unit 102 or theextension unit 103.

The remote unit 602 can include a processor 608 configured to execute asuitable algorithm for determining whether to switch between a transmitmode to a receive mode. The remote unit 602 can also include atransceiver 604 that has a switching module 606 for switching the remoteunit 602 between a transmit mode for transmitting device-to-device and areceive mode. The switching module 606 can include one or more switchesthat can be configured by the transceiver in response to control signalsreceived from the processor 608. The remote unit 602 can also include asignal processing module 610 that can perform one or more signalprocessing functions, as previously described with respect to the signalprocessing module 208 in FIG. 2.

In some aspects, the device-to-device communication can involve asimplex operation (e.g., push-to-talk). In some aspects, thedevice-to-device communication can be a duplex operation.

In the simplex case, at least one remote unit 602 can be set to a“receive” mode for receiving signals from a first terminal device and atleast one additional remote unit 602 can be set to a “transmit” mode fortransmitting signals to a second terminal device. One or more remoteunits 602 near a transmitting terminal device can be set to a receivemode for receiving signals from the terminal device. Other remote units602 that are further from the transmitting terminal device can be set toa transmit mode for transmitting the signals to a receiving terminaldevices.

In some aspects, a remote unit 602 can switch between a transmit modeand a receive mode based on a signal level of signals received from atransmitting terminal device. For a received signal level above athreshold, a remote unit 602 can switch to a receive mode. For areceived signal level below a threshold, the remote unit 602 can switchto a transmit mode. In additional or alternative aspects, signalsreceived at multiple remote units 602 from a terminal device can beanalyzed to estimate or otherwise determine a geographic location of theterminal device. One or more remote units 602 can be identified as beinglocated at less than at a threshold distance from the geographiclocation of the terminal device. The one or more remote units 602located at less than a threshold distance from the terminal device canswitch to a receive mode.

In some aspects, the remote units 602 can switch from a device-to-devicemode to a standard operation mode in the absence of device-to-devicecommunication. A standard operation mode can include the remote units602 transmitting uplink signals received from terminal devices to masterunits 102 of the DAS 100. For example, if all simplex terminal devicesin a DAS 100 are idle, all remote units 602 can switch to a standardoperation mode.

In some aspects, a master unit 102 can coordinate device-to-devicecommunication via multiple remote units 602. When a terminal devicestarts to transmit within the DAS 100 coverage area, one or more remoteunits 602 can receive the signal from the terminal device. The masterunit 102 can monitor signals received by the remote units 602. Themaster unit 102 can detect that a received signal from a given remoteunit 602 has a signal level above a minimum defined level (e.g., anun-squelch threshold). The master unit 102 can combine a signal having asignal level above the threshold that is received from a remote unit 602with other signals having signal levels above the threshold that arereceived from other remote units 602. For example, received signalshaving signals above the threshold can be added together into acomposite sum. The combined signal can be transmitted to remote units602 that are not receiving the signal above the threshold.

In some aspects, a terminal device can move between different coveragezones serviced by different remote units 602. As the transmitting devicemoves, a signal level of a signal transmitted by the terminal device mayrise above and fall below a specified threshold at different remoteunits 602. If a signal level for a given remote unit 602 falls below thethreshold, the master unit 102 can exclude or otherwise omit that signalfrom the summing operation. The master unit 102 can configure the remoteunit 602 to switch from a receive mode to a transmit mode. Thetransceiver 604 of the remote unit 602 can be switched to a transmitmode for transmitting the newly reconfigured summed signal. Conversely,if a signal level for a given remote unit 602 rises above the threshold,the master unit 102 can add that signal to the summing operation. Themaster unit 102 can configure the remote unit 602 to switch from atransmit mode to a receive mode.

The master unit 102 can configure the remote unit 602 by transmittingcontrol signals to a remote unit 602. The processor 608 can configurethe transceiver 604 in response to the control signals. For example, ifa master unit 102 determines that the remote unit 602 is receivingsignals having signal levels above the threshold signal level (e.g., asa result of a simplex terminal device being keyed), the master unit 102can provide a control signal that instructs the remote unit 602 toswitch to a transmit mode. The transceiver 604 of the remote unit 602can be switched to the transmit mode by the processor 608 in response tothe control signal. If the master unit 102 determines that the remoteunit 602 is receiving signals having signal levels below the thresholdsignal level (e.g., as a result of a simplex terminal device beingun-keyed), the master unit 102 can provide an additional control signalthat instructs the remote unit 602 to switch from the transmit mode to areceive mode. The transceiver 604 of the remote unit 602 can be switchedto the receive mode by the processor 608 in response to the additionalcontrol signal.

In some aspects, a remote unit 602 may be configured to transmit signalsand receive signals on the same frequency. The remote unit 602 candistinguish between signals received from a terminal device and signalstransmitted by the remote unit 602 itself by adding a frequency shift tothe signals transmitted by the remote unit 602. The frequency shift cande-correlate signals transmitted by the remote unit 602 from signalsreceived from the terminal device. A received signal received from aterminal device can be distinguished from the signals that aretransmitted by the remote unit.

In some aspects, one or more signals received by a remote unitconfigured for device-to-device communication can be transmitted to abase station or other telecommunication device via the master unit 102.For example, a master unit 102 can be communicatively coupled to one ormore other DAS's. One or more signals received by a remote unitconfigured for device-to-device communication can communicated to otherremote units 602 and to the master unit 102 that is communicativelycoupled to the one or more other DAS's.

The foregoing description of the examples, including illustratedexamples, of the invention has been presented only for the purpose ofillustration and description and is not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Numerousmodifications, adaptations, and uses thereof will be apparent to thoseskilled in the art without departing from the scope of this invention.The illustrative examples described above are given to introduce thereader to the general subject matter discussed here and are not intendedto limit the scope of the disclosed concepts.

What is claimed is:
 1. A distributed antenna system comprising: a masterunit having first circuitry; a first remote unit having second circuitryand communicatively coupled to the master unit; a second remote unithaving third circuitry and communicatively coupled to the master unit;wherein the first remote unit is configured to: receive downlink RFsignals from a base station; and provide downlink signals to the masterunit; and wherein the master unit is configured to: transmit thedownlink signals received from the first remote unit to the secondremote unit; and instruct the first remote unit to establish acommunication link with the base station in response to detecting amalfunction with respect to an additional communication link between themaster unit and an additional base station.
 2. The distributed antennasystem of claim 1, wherein the master unit is further configured to:communicate signals between an additional base station and the secondremote unit.
 3. The distributed antenna system of claim 1, wherein thefirst remote unit is further configured: to communicate RF signalsbetween the master unit and the terminal device.
 4. The distributedantenna system of claim 3, wherein the first remote unit includes: afirst duplexer configured to isolate downlink RF signals transmitted tothe terminal device from uplink RF signals received from the terminaldevice; and a second duplexer configured to isolate the uplink RFsignals transmitted to the base station from downlink RF signalsreceived from the base station.
 5. The distributed antenna system ofclaim 3, wherein the first remote unit comprises: a configurableisolation sub-system that is configured to operate in a first mode and asecond mode, wherein the configurable isolation sub-system is configuredto: isolate downlink RF signals transmitted to the terminal device fromuplink RF signals received from the terminal device when operating inthe first mode; and isolate the uplink RF signals transmitted to thebase station from downlink RF signals received from the base station. 6.The distributed antenna system of claim 5, wherein the configurableisolation sub-system includes: at least one configurable filterconfigured to: attenuate signals outside of a first frequency band forreceiving the downlink RF signals from the base station when operatingin the first mode; and attenuate signals outside of a second frequencyband for receiving the uplink RF signals from the terminal device whenoperating in the second mode.
 7. The distributed antenna system of claim1, wherein the first remote unit is further configured to: receive asignal from the terminal device; and provide the signal to the masterunit; wherein the master unit is further configured to: provide thesignal received from the first remote unit to the second remote unit;wherein the second remote unit is configured to: transmit the signal toat least one additional terminal device.
 8. The distributed antennasystem of claim 1, wherein each of the first and second remote units isfurther configured to: identify the base station by scanning downlinkfrequency bands; and detect signal traffic from the base station in atleast one of the scanned downlink frequency bands; wherein the masterunit is further configured to configure the first remote unit toestablish the communication link with the base station based on thesignal traffic detected by the first remote unit exceeding a thresholdsignal level or satisfying specified signal quality criteria.
 9. Thedistributed antenna system of claim 8, wherein the master unit isfurther configured to respond to detecting a cessation of themalfunction by configuring the first remote unit to terminate thecommunication link with the base station.
 10. The distributed antennasystem of claim 1, wherein the first remote unit is further configuredto: convert the RF signals received from the base station to thedownlink signal provided to the master unit.
 11. A remote unit of adistributed antenna system, the remote unit comprising: a transceiverconfigured to: communicate RF signals between a master unit of thedistributed antenna system and a terminal device; and receive downlinkRF signals from a base station; and signal processing circuitryconfigured to: provide downlink signals to the master unit; wherein theremote unit receives instructions from a host unit of the distributedantenna system to establish a communication link with the base stationin response to detecting a malfunction with respect to an additionalcommunication link between the master unit and an additional basestation.
 12. The remote unit of claim 11, wherein the remote unitfurther comprises: a first duplexer configured to: isolate downlink RFsignals transmitted to the terminal device from uplink RF signalsreceived from the terminal device; and a second duplexer configured to:isolate the uplink RF signals transmitted to the base station fromdownlink RF signals received from the base station.
 13. The remote unitof claim 11, wherein the remote unit further comprises: a configurableisolation sub-system that is configured to operate in a first mode and asecond mode, wherein the configurable isolation sub-system is configuredto: isolate downlink RF signals transmitted to the terminal device fromuplink RF signals received from the terminal device when operating in afirst mode; and isolate the uplink RF signals transmitted to the basestation from downlink RF signals received from the base station.
 14. Theremote unit of claim 13, wherein the configurable isolation sub-systemincludes: at least one configurable filter configured to: attenuatesignals outside of a first frequency band for receiving the downlink RFsignals from the base station when operating in the first mode; andattenuate signals outside of a second frequency band for receiving theuplink RF signals from the terminal device when operating in the secondmode.
 15. The remote unit of claim 11, wherein the signal processingcircuitry is further configured to: convert the RF signals received fromthe base station to the downlink signal provided to the master unit. 16.A distributed antenna system for providing device-to-devicecommunication, the distributed antenna system comprising: a first remoteunit having first circuitry, the first remote unit configured to:receive a signal from a first base station; detect that the signal isreceived at a signal level that exceeds a threshold signal level; andswitch to a receive mode for receiving signals from the first basestation based on the signal level exceeding the threshold signal level;receive an additional signal from the first base station; detect thatthe additional signal is received at an additional signal level thatdoes not exceed the threshold signal level; and switch to a transmitmode for transmitting signals to the second terminal device based on theadditional signal level not exceeding the threshold signal level; asecond remote unit having second circuitry, the second remote unitconfigured to transmit the signal to a second terminal device; and amaster unit having third circuitry and communicatively coupled to thefirst and second remote units, the master unit configured to receive thesignal from the first remote unit and provide the signal to the secondremote unit for transmission to the second terminal device.
 17. Thedistributed antenna system of claim 16, wherein the master unit isfurther configured to: determine that the first base station is closerto a first geographical location of the first remote unit than a secondgeographical location of the second remote unit; and based on the firstbase station being closer to the first geographical location: set thefirst remote unit to a receive mode for receiving signals from the firstbase station; and set the second remote unit to a transmit mode fortransmitting signals to the second terminal device.
 18. The distributedantenna system of claim 16, wherein the first remote unit comprises aplurality of remote units configured to receive the signal from thefirst base station, wherein the master unit is further configured to:receive the signal from each of the plurality of remote units; combinethe signals received from the plurality of remote units into a combinedsignal; and provide the combined signal to the second remote unit fortransmission to the second terminal device.
 19. The distributed antennasystem of claim 16, wherein the first remote unit is further configuredto: receive downlink RF signals from a base station; and providedownlink signals to the master unit; wherein the master unit isconfigured to transmit the downlink signals received from the firstremote unit to the second remote unit.
 20. The distributed antennasystem of claim 19, wherein the first remote unit is further configuredto: convert the downlink RF signals received from the base station tothe digital downlink signals provided to the master unit.